The term used is the common word for setting free
(Acts 2:24; Revelation 1:5). The concept indicates that the seal over the lock of the abyss will be broken, the key inserted so as to open the door and the chain currently binding Satan be removed. Note that the passage does not say that Satan will escape; it says that he will be set free, which means that God remains in sovereign control over Satan. The Lord will allow Satan to deceive the nations who had heard the gospel through the work of the white horse. The Holy Spirit will tell us more about this in Revelation 20:7.
3 and threw him into the pit, and shut it and sealed it over him, so that he might not deceive the nations any longer, until the thousand years were ended. After that he must be released for a little while.